Optically active 1,2-bis(alkylmethylphosphino)ethanes and bis(alkylmethylphosphino)methanes are unique diphosphine ligands combining the simple molecular structure and P-stereogenic asymmetric ...environment. This work shows that these ligands exhibit excellent enantioselectivity in rhodium-catalyzed asymmetric hydrogenation of α,β-unsaturated phosphonic acid derivatives. The enantioselective hydrogenation mechanism elucidated by NMR study is also described.
ABSTRACT
Purpose
To investigate mechanisms governing the stabilization and destabilization of immunoglobulin (IgG1) by arginine (Arg).
Methods
The effects of Arg on the aggregation/degradation, ...thermodynamic stability, hydrophobicity, and aromatic residues of IgG1 were respectively investigated by size-exclusion chromatography, differential scanning calorimetry, probe fluorescence, and intrinsic fluorescence.
Results
Arg monohydrochloride (Arg–HCl) suppressed IgG1 aggregation at near-neutral pH, but facilitated aggregation and degradation at acidic pH or at high storage temperature. Equimolar mixtures of Arg and aspartic acid (Asp) or glutamic acid (Glu) suppressed aggregation without facilitating degradation even at high temperature. Arg–HCl decreased the thermodynamic stability of IgG1 by enthalpic loss, which was counteracted by using Asp or Glu as a counterion for Arg. The suppression of aggregation by Arg–HCl was well correlated with the decrease in hydrophobicity of IgG1. The intrinsic fluorescence of IgG1 was unaffected by Arg–HCl.
Conclusions
Suppression of IgG1 aggregation can be attributed to the interaction between Arg and hydrophobic residues; on the other hand, facilitation of aggregation and degradation is presumably due to the interaction between Arg and some acidic residues, which could be competitively inhibited by simultaneously adding either Asp or Glu.
We report a case of cerebellum abscess due to
(
) in a 60-year-old man. He was admitted to our hospital complaining of headache and dizziness. On admission, he was lucid with the following vital ...data:blood pressure, 136/89 mmHg;heart rate, 65 beats/min;body temperature, 37.0℃;and oxygen saturation, 100%. He had a moderate headache and could not walk straight. In general, there were no abnormal findings except for his poor dental hygiene. Laboratory findings revealed elevated white blood cell counts(10,900/mm
)and brain MRI revealed a mass shadow that was suspected to be an abscess in the left side of his cerebellum. Elective surgery was scheduled. However, consciousness of disorder was observed on the second hospital day and the size of mass shadow extended;hence, emergent drainage under craniotomy was performed. The diagnosis was cerebellum abscess, and
, which is a normal flora in the oral cavity, was isolated in his cerebellum abscess. After the surgery, his hospital course was positive under the treatment of antibiotics for
. The route of bacterial infection entry was unclear;however, it will be considered that abscesses in the central nervous system occur because of poor dental hygiene.
The asymmetric hydrogenation of aryl- and alkyl-substituted enamides catalyzed by Rh-BisP* complex affords optically active amides with very high ee values. The Rh-MiniPHOS catalyst gives somewhat ...less satisfactory results. Hydrogenation of the aryl-substituted enamides with (S,S)-BisP*-Rh catalyst gives R-amides, whereas the t-Bu- and 1-adamantyl-substituted enamides give S-products with 99% ee. Reaction of Rh(BisP*)(CD3OD)2BF4 (11) with CH2C(C6H5)NHCOCH3 (5) gives two diastereomers of the catalyst−substrate complex (12a,b), which interconvert reversibly by both intra- and intermolecular pathways as shown by EXSY data. Only one isomer in equilibrium with solvate complex 11 was detected for each of the catalyst−substrate complexes 17 and 18 obtained from CH2C(t-Bu)NHCOCH3 (6) or CH2C(1-adamantyl)NHCOCH3 (7). Hydrogenation of these equilibrium mixtures at −100 °C gave monohydride intermediates 19 and 20, respectively. In these monohydrides the Rh atom is bound to the β-carbon. A new effect of the significant decrease of ee was found for the asymmetric hydrogenation of CH2C(C6H4OCH3-o)NHCOCH3 (21), when H2 was substituted for HD or D2.
Excellent enantioselectivities up to 99.7% were achieved in the hydrogenation of (E)-β-(acylamino)acrylates by the use of Rh(I)-complexes of electron-rich diphosphines, t-Bu-BisP* and t-Bu-MiniPHOS. ...Low-temperature NMR experiments testify that monohydrides with β-carbon atom of the substrate bound to rhodium are involved in the catalytic cycle.
A new class of chiral C2‐symmetric bis(trialkyl)phosphine ligands has been prepared and used in Rh(I)‐catalyzed asymmetric hydrogenation reactions. The ligands, 1,2‐bis(alkylmethylphosphino)ethanes ...1a‐g(abbreviated as BisP*, alkyl = t‐butyl, 1‐adamantyl, 1‐methylcyclohexyl, 1,1‐diethylpropyl, cyclopentyl, cyclohexyl, isopropyl) and 1,2‐bis(alkylmethylphosphino)methanes 2a‐d(abbreviated as MiniPHOS, alkyl = t‐butyl, cyclohexyl, isopropyl, phenyl) are prepared by a simple synthetic approach based on the air‐stable phosphine–boranes. These new ligands give the corresponding Rh(I) complexes, which are effective catalytic precursors for the asymmetric hydrogenation of a representative series of dehydroamino acids and itaconic acid derivatives. Enantioselectivities observed in these hydrogenations are universally high and in many cases exceed 99%. X‐Ray characterization of four precatalysts, study of the pressure effects, deuteration experiments, and characterization of the wide series of intermediates in the catalytic cycle are used for the discussion of the possible correlation between the structure of the catalysts and the outcome of the catalytic asymmetric hydrogenation.
Skeletal muscles include fast and slow muscle fibers. The tibialis anterior muscle (TA) is mainly composed of fast muscle fibers, whereas the soleus muscle (SOL) is mainly composed of slow muscle ...fibers. However, a noninvasive approach for appropriately investigating the characteristics of muscles is not available. Monitoring of skeletal muscle characteristics can help in the evaluation of the effects of strength training and diseases on skeletal muscles.
The present study aimed to determine whether q-space imaging can distinguish between TA and SOL in in vivo mice.
In vivo magnetic resonance imaging of the right calves of mice (n = 8) was performed using a 7-Tesla magnetic resonance imaging system with a cryogenic probe. TA and SOL were assessed. q-space imaging was performed with a field of view of 10 mm × 10 mm, matrix of 48 × 48, and section thickness of 1000 μm. There were ten b-values ranging from 0 to 4244 s/mm2, and each b-value had diffusion encoding in three directions. Magnetic resonance imaging findings were compared with immunohistological findings.
Full width at half maximum and Kurtosis maps of q-space imaging showed signal intensities consistent with immunohistological findings for both fast (myosin heavy chain II) and slow (myosin heavy chain I) muscle fibers. With regard to quantification, both full width at half maximum and Kurtosis could represent the immunohistological findings that the cell diameter of TA was larger than that of SOL (P < 0.01).
q-space imaging could clearly differentiate TA from SOL using differences in cell diameters. This technique is a promising method to noninvasively estimate the fiber type ratio in skeletal muscles, and it can be further developed as an indicator of muscle characteristics.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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